Error Analysis of Space Manipulator Joint Module Based on the SDT Theory

An error model based on the Small Displacement Torsor (SDT) theory was developed to analyze the influence of errors in manufacturing and assembly on the space manipulator. Geometric and assembly error models were developed using the SDT method; the homogeneous coordinate transformation method was used to develop the error propagation model; and the joint output error was derived. A Monte Carlo simulation was conducted to calculate the distribution probability of the output error, and a sensitivity analysis for critical tolerances was performed. The relationship between the bearing fit clearance and temperature was established based on a simplified finite element model, which was then used to evaluate the influence of temperature on the joint output point. It is found that the joint output position error is distributed approximately normally in the x and y directions, and randomly in the z direction; all of the angular errors are normally distributed; the comprehensive output error is 0.23 mm, which can satisfy the design requirement. As the temperature increases, the fit clearance between the bear and shell increases significantly, causing bear fitting to change from transition fit to clearance fit and resulting in an increase of 21.7% in output error.